There are two general types of concrete pipe making machines known as packerhead and vibrating core machines. Packerhead concrete pipe making machines have rotating packerheads that are moved up into molds to form concrete pipes. An example of a packerhead concrete pipe making machine having a counter rotating packerhead is shown by Fosse in U.S. Pat. No. 4,407,648. The vibrating core concrete pipe making machines have generally cylindrical cores accommodating vibrators. The cores are moved up into molds to form concrete pipes. The vibrators operate to consolidate and densify the concrete in the molds during the forming of the pipes. The vibrating core concrete pipe making machine is generally slower in operation than a packerhead concrete pipe making machine. An example of a vibrating core concrete pipe making machine is shown by Fosse et al in U.S. Pat. No. 3,948,354.
The vibration process is a relativly slow method of making concrete pipe. However, the vibration process produces denser pipes and does not twist the cages. The packerhead process is fast in operation and can result in reinforcing cage twist. The packerhead process produces concrete pipes having smooth outside and inside finishes. The outside finish of pipes made by vibrations process is not smooth due to a tendancy of air pockets to collect between the outside walls of the pipes and the molds.